Effect of uremic human plasma on renin activity.

Abstract

(1) Pressor responses to norepinephrine, synthetic angiotensin II and hog renin in rats were compared before and after isovolemic transfusion of human plasma. After transfusion of plasmas from normal subjects and a hypertensive patient with normal renal function, the pressor response to hog renin in the assay rat somewhat decreased with comparable decrease of responsiveness to norepinephrine. With plasma from a normotensive patient with azotemia, the response to renin remained unchanged with decreased responsiveness to norepinephrine and angiotensin II. Of 7 studies with plasmas from 5 hypertensive patients with terminal uremia, 4 revealed aug-mented responses to hog renin in spite of decreased sensitivity to norepine-phrine in all the 4 and angiotensin II in 2 of them.(2) The amounts of angiotensin formed during incubation of a fixed dose of hog renin and an excess of renin-substrate in the presence of plasmas from uremic and/or hypertensive patients were compared with those of simultaneous incubation in the presence of normal human plasmas. In-cubation with neutral mixtures resulted in significantly greater yields of angio-tensin in 6 studies with plasmas from 4 hypertensive uremic patients as com-pared to those with control plasmas. Incubation with acidified mixtures caused formation of angiotensin in significantly greater amounts in 2 studies. Incubation studies with plasmas from a hypertensive patient without renal failure and a normotensive patient with impaired renal function revealed no significant difference between yields of angiotensin with patients' plasmas and those with control plasmas.(3) The results suggest that the activity of a given dose of renin may be greater in the presence of plasma from a patient with terminal uremia and hypertension than in the presence of plasma from a normal man. The observed phenomena are quite similar with those known to occur with plasma from renoprival animals.